Physiological Control of Gene Expression in a Seasonal Polyphenism

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Some species of animals occur in two different morphologies, a phenomenon called polyphenism. Usually the different alternative morphologies develop in different seasons of the year. In order to develop a different morphology it is necessary to activate a different set of genes, and thus the problem of control of polyphenism is to discover the mechanism by which an animal "chooses" between two alternative gene sets. The aim of the proposed research is to develop, for the first time, an understanding of complete pathway of genetic control in such a seasonal polyphenism. For this research we will use the butterfly, Precis coenia, which has a dramatic color polyphenism and for which our preliminary studies have already elucidated portions of the control pathway. The proposed research will identify the pigments responsible for the different color forms and the enzymes responsible for their synthesis. The genes for these enzymes will then be cloned so that we may develop tools to study the mechanism by which their expression is controlled. We know that a steroid hormone, 20-OH-ecdysone, is ultimately responsible for stimulating the genetic switch that causes the alternative pigment synthesis to occur, and experiments will be done to begin to investigate how this could control the differential expression of enzymes for the alternative pigments.